In the case of ABS (anti-lock brake system) or traction control system, for example, it is necessary to monitor the output stages and the downstream solenoid valves for faults which occur. Today, so-called intelligent output stages, also called power circuit breakers, are on the market which exhibit a feedback. Reference may be made here, for example, to the power circuit breakers TLE4224 and TLE5224 by Siemens and to U577 by SGS Thomson. It emerges from the provisional specification of TLE4224, that these power circuit breakers are used to signal faults such as, for example, undervoltage, loss of power, short circuits to earth in the operating and quiescent state of the circuit breaker, and short circuits to battery voltage in the case of an activated circuit breaker. In addition to inductive loads, ohmic loads (e.g. a heat source) can also be monitored.